Only 460hp

I agree the OP's results seem fairly reasonable for the heads and cam combo. As others have said, more CR, more cam, and more head flow are in order if you want more output. I don't know about the step headers. Others may have better Intel on them.

Me? I'm a big fan of a SFT cam. My 408 has a 251/[email protected] SFT. If I had to do it again, I'd go a skosh bigger - maybe something like a [email protected]. It's pretty rough at idle (my wife loves it!) but still idles at about 850-900 and as Rat Bastid said, the 4" stroke can handle cam duration! My engine made 503 #-ft @ 3500 rpm and that's the only point that was recorded as after that, the et slip will tell you what you need to know. (We spotted it in at higher RPM's with other engines tested on the same dyno with similar parts so have a good estimate what it makes. But the et slip is a better indicator for me.

I have a thread called The 72 Demon Follies if you want to see more details on the combo but the car has gone a best of [email protected] .

I'll keep tuning on it but I am limited by the Eddie RPM heads and then the cam. I suspect your engine is too. Anyhow, I share just so you can see what someone else has done. Learn from it and do better!!